The Degradation Rate of Straw Returned to Limestone Soil and the Effect on Soil Fertility

Abstract

Limestone soil is a poor quality soil with a low rate of nutrient supply due to the accumulation of organic carbon. Here, we examined the degradation of maize straw in limestone soil and red soil using indoor simulation. Dynamic testing was conducted on soil chemical properties and soil fertility. We found that the degradation rate of straw in karst soil is higher than for non-karst soil. The highest degradation rate of straw occurred during the first 60 d, after which it rose slowly and balanced out at 98 d. The peak value of degradation of straw in karst soil was found at 28 d, while that in non-karst soil occurred at 42 d. The total period of degradation lasted 160 d; the degradation rate of straw in karst soil and non-karst soil was 77% and 75%, respectively. During the period of straw degradation, the pH of soil tended to decrease in the early stage and rise slowly in later stages and this is consistent with the pattern of degradation products during different stages of straw degradation. Straw return to fields can increase soil fertility, and the growth rate of available N and K content is significant. Compared to karst soil, the content of various fertility indicators in non-karst areas were lower according to total content tests, although the increase (percentage) in nonkarst area was higher; available P and K content were found to be higher in non-karst areas according to availability tests. Some available nutrients in straw return can be more readily released in non-karst soil, while karst soil can contribute to the accumulation of total nutrient content due to its special soil texture features, the firm binding of many nutrients with clay minerals and the slow supply of nutrients.